I have an Intel I7-3930k system. I have my preferences set to use at most 50% of the CPUs, 30% of CPU time. What I have noticed, especially today is that with 5 separate tasks, all of which are SETI@home Enhanced 6.03 the CPU fan is cycling anywhere from 500 to 600 RPM and the CPUs in use seems to jump between the 12 possible threads. Is there anything I can do to try and make the load more steady?

Not use BOINC its throttling. BOINC throttles applications by suspending them and resuming them per 10 seconds. So in your case 7 seconds of rest, 3 seconds of running. Due to BOINC its source code being available for many platforms without relying on a special programming, the developers can't add another throttle function that uses e.g. the Windows app pausing function as this won't compile on Linux or the Mac.

http://efmer.eu/boinc/: The program runs on Windows 2003 / Windows XP / Vista/ Windows 7. There is a 32 and a 64 Bit installer. Works on Intel and AMD machines.
This one runs in a GUI, which may be easier to do than Threadmaster.

http://threadmaster.tripod.com/: Run on Windows 2000 and above.
This includes Windows 7. This one runs from the registry. It's just that Threadmaster is a very old program, its developer has probably never been back to his site to update it for newer Windows versions.
____________Jord